Mercurial > hg > octave-nkf
view scripts/control/system/tf2ss.m @ 4771:b8105302cfe8
[project @ 2004-02-16 17:45:50 by jwe]
author | jwe |
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date | Mon, 16 Feb 2004 17:45:50 +0000 |
parents | 22bd65326ec1 |
children | bdbee5282954 |
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## Copyright (C) 1996, 1998 Auburn University. All rights reserved. ## ## This file is part of Octave. ## ## Octave is free software; you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by the ## Free Software Foundation; either version 2, or (at your option) any ## later version. ## ## Octave is distributed in the hope that it will be useful, but WITHOUT ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License ## for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, write to the Free ## Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111 USA. ## -*- texinfo -*- ## @deftypefn {Function File} {} tf2ss (@var{inputs}) ## @format ## Conversion from tranfer function to state-space. ## The state space system ## . ## x = Ax + Bu ## y = Cx + Du ## ## is obtained from a transfer function ## ## num(s) ## G(s)=------- ## den(s) ## ## via the function call [a,b,c,d] = tf2ss(num,den). ## The vector 'den' must contain only one row, whereas the vector 'num' ## may contain as many rows as there are outputs of the system 'y'. ## The state space system matrices obtained from this function will be ## in controllable canonical form as described in "Modern Control Theory", ## [Brogan, 1991]. ## ## ## @end format ## @end deftypefn ## Author: R. Bruce Tenison <btenison@eng.auburn.edu> ## Created: June 22, 1994 ## mod A S Hodel July, Aug 1995 function [a, b, c, d] = tf2ss (num, den) if(nargin != 2) error("tf2ss: wrong number of input arguments") elseif(isempty(num)) error("tf2ss: empty numerator"); elseif(isempty(den)) error("tf2ss: empy denominator"); elseif(!isvector(num)) error(sprintf("num(%dx%d) must be a vector",rows(num),columns(num))); elseif(!isvector(den)) error(sprintf("den(%dx%d) must be a vector",rows(den),columns(den))); endif ## strip leading zeros from num, den nz = find(num != 0); if(isempty(nz)) num = 0; else num = num(nz(1):length(num)); endif nz = find(den != 0); if(isempty(nz)) error("denominator is 0."); else den = den(nz(1):length(den)); endif ## force num, den to be row vectors num = vec(num)'; den = vec(den)'; nn = length(num); nd = length(den); if(nn > nd) error(sprintf("deg(num)=%d > deg(den)= %d",nn,nd)); endif ## Check sizes if (nd == 1) a = []; b = []; c = []; d = num(:,1) / den(1); else ## Pad num so that length(num) = length(den) if (nd-nn > 0) num = [zeros(1,nd-nn), num]; endif ## Normalize the numerator and denominator vector w.r.t. the leading ## coefficient d1 = den(1); num = num / d1; den = den(2:nd)/d1; sw = nd-1:-1:1; ## Form the A matrix if(nd > 2) a = [zeros(nd-2,1),eye(nd-2,nd-2);-den(sw)]; else a = -den(sw); endif ## Form the B matrix b = zeros(nd-1,1); b(nd-1,1) = 1; ## Form the C matrix c = num(:,2:nd)-num(:,1)*den; c = c(:,sw); ## Form the D matrix d = num(:,1); endif endfunction